ing chrysalis stage and later
emerges with wings. The development of insects is therefore extremely
complicated.

[Illustration: The chinch bug showing development with incomplete
metamorphosis; a, egg; b, first nymph; c, second nymph; d, third nymph;
e, fourth nymph; f, adult winged bug; g, chinch bugs extracting sap from
corn plant. To control this pest burn over all winter harboring places
and use chemical or dust barriers following wheat harvest.]

_The Principal Orders_

In order to study a group of animals which includes so many thousand
different kinds it is necessary to divide them into a number of sharply
defined divisions or orders. All animal life is naturally grouped into
such divisions and subdivisions. Among the insects we at once detect
seven large, sharply defined divisions or orders, and ten or more
smaller ones. Of these we have first, the two-winged true flies; second,
the four-winged butterflies and moths; third, the hard-backed beetles;
fourth, the stinging four-winged wasps and bees; fifth, the variously
formed sucking insects or true bugs, as chinch bugs and bed-bugs; sixth,
the rapid-flying four-winged snake doctors or dragon-flies and, seventh,
the hopping forms, the grasshoppers. Besides these we have the various
smaller orders of water-loving insects, fleas, etc. The seven groups
mentioned above include the majority of our common forms and in the
studies to follow we will include only representatives from these
orders.

[Illustration: The Hessian fly showing development with complete
metamorphosis; a, egg; b, larva or maggot; c, flax-seed stage; d, pupa;
e, adult winged fly; f, wheat stubble with flax-seed stages near base
taken after harvest. To control this pest, plow under stubble after
harvest; keep down all volunteer wheat and sow wheat after fly-free date
in the fall.]

_Their Habits_

The habits of insects are as varied as their forms and adaptations. Some
live in the water all their life, others spend a part of their life
under water, others live the care-free life of the open air, others
enjoy feeding upon and living in the foulest of filth, others associate
themselves with certain definite crops or animals thereby doing untold
injury, while others produce food and other materials which are to be
used by man for his comfort. Every imaginable nook and crook, from the
depths of lakes to the tops of mountains, from the warm, sunny south to
the cold frigid north, from the foul